Light-emitting diode packages with directional emission intensity and color uniformity

ABSTRACT

Light-emitting diode (LED) packages and more particularly LED packages with directional emission intensity and color uniformity are disclosed. LED packages include one or more LED chips on a submount with arrangements of light-altering materials and lumiphoric material layers that provide directional light emissions with improved color over angle uniformity. Light-altering materials are provided that cover sidewalls of LED chips while lumiphoric material layers cover LED chips and light-altering materials. Such LED packages may avoid the need to include encapsulation materials and/or lenses that would otherwise cover the lumiphoric material layers. As such, exterior light-exiting faces of LED packages are formed by surfaces of lumiphoric material layers.

FIELD OF THE DISCLOSURE

The present disclosure relates to light-emitting diode (LED) packagesand more particularly to LED packages with directional emissionintensity and color uniformity.

BACKGROUND

Solid-state lighting devices such as light-emitting diodes (LEDs) areincreasingly used in both consumer and commercial applications.Advancements in LED technology have resulted in highly efficient andmechanically robust light sources with a long service life. Accordingly,modern LEDs have enabled a variety of new display applications and arebeing increasingly utilized for general illumination applications, oftenreplacing incandescent and fluorescent light sources.

LEDs are solid-state devices that convert electrical energy to light andgenerally include one or more active layers of semiconductor material(or an active region) arranged between oppositely doped n-type andp-type layers. When a bias is applied across the doped layers, holes andelectrons are injected into the one or more active layers where theyrecombine to generate emissions such as visible light or ultravioletemissions. An LED chip typically includes an active region that may befabricated, for example, from silicon carbide, gallium nitride, galliumphosphide, indium phosphide, aluminum nitride, gallium arsenide-basedmaterials, and/or from organic semiconductor materials. Photonsgenerated by the active region are initiated in all directions.

Lumiphoric materials, such as phosphors, may be arranged in lightemission paths of LED emitters to convert portions of light to differentwavelengths. LED packages have been developed that can providemechanical support, electrical connections, and encapsulation for LEDemitters. Light emissions that exit surfaces of LED emitters typicallyinteract with various elements or surfaces of the LED package andlumiphoric materials before exiting, thereby increasing opportunitiesfor light loss and potential non-uniformity of light emissions. As such,there can be challenges in producing high quality light with desiredemission characteristics while also providing high light emissionefficiency in LED packages.

The art continues to seek improved LEDs and solid-state lighting deviceshaving desirable illumination characteristics capable of overcomingchallenges associated with conventional lighting devices.

SUMMARY

Aspects disclose herein relate to light-emitting diode (LED) packagesand more particularly to LED packages with directional emissionintensity and color uniformity. LED packages include one or more LEDchips on a submount with arrangements of light-altering materials andlumiphoric material layers that provide directional light emissions withimproved color over angle uniformity. Light-altering materials areprovided that cover sidewalls of LED chips while lumiphoric materiallayers cover LED chips and light-altering materials. Such LED packagesmay avoid the need to include encapsulation materials and/or lenses thatwould otherwise cover the lumiphoric material layers. As such, exteriorlight-exiting faces of LED packages are formed by surfaces of lumiphoricmaterial layers.

In one aspect, an LED package comprises: a submount; at least one LEDchip on the submount, the at least one LED chip including a first side,a second side that is mounted to the submount, and peripheral edges thatbound the first side and the second side; a light-altering material onthe peripheral edges of the at least one LED chip and on portions of thesubmount that are adjacent the at least one LED chip; and a lumiphoricmaterial layer on the at least one LED chip and the light-alteringmaterial, wherein a surface of the lumiphoric material layer forms anexterior light-exiting face for the LED package. In certain embodiments,the lumiphoric material layer, the light-altering material, and thesubmount collectively form a peripheral edge of the LED package. Incertain embodiments, the lumiphoric material layer comprises a thicknessof no more than 150 microns (μm), or in a range from 50 μm to 100 μm. Incertain embodiments, a perpendicular distance from the first side of theLED chip to the exterior light-exiting face is no more than 100 microns(μm), or in a range from 50 μm to 100 μm. In certain embodiments, thelight-altering material covers the peripheral edges of the at least oneLED chip. In certain embodiments, a height of the light-alteringmaterial above the submount decreases in a lateral direction away fromthe peripheral edges of the at least one LED chip. In certainembodiments, the lumiphoric material layer extends on a portion of thelight-altering material with the height that decreases in the lateraldirection away from the peripheral edges of the at least one LED chipsuch that a portion of the lumiphoric material layer is closer to thesubmount than the first side of the at least one LED chip. In certainembodiments, the lumiphoric material layer comprises phosphor particlesin a binder with a volume percentage of phosphor particles in a rangefrom 25% to 45%. In certain embodiments, the exterior light-exiting facefor the LED package is configured to form an interface with an ambientatmosphere that is separate from the LED package.

In another aspect, an LED package comprises: a submount comprising afirst side and a second side that opposes the first side, the first sidecomprising metal traces, and the second side comprising package bondpads that are electrically coupled to the metal traces; at least one LEDchip including a first side and a second side that is mounted on andelectrically coupled to the metal traces; and a lumiphoric materiallayer on the at least one LED chip such that a surface of the lumiphoricmaterial layer forms an exterior light-exiting face for the LED packageand a perpendicular distance from the first side of the LED chip to theexterior light-exiting face is no more than 100 μm. In certainembodiments, the perpendicular distance from the first side of the LEDchip to the exterior light-exiting face is in a range from 50 μm to 100μm. The LED package may further comprise a light-altering material onportions of the submount that are adjacent the at least one LED chip,wherein the light-altering material is arranged between the lumiphoricmaterial layer and the submount. In certain embodiments, a height of thelight-altering material above the submount decreases in a lateraldirection away from the at least one LED chip. In certain embodiments,the lumiphoric material layer extends on a portion of the light-alteringmaterial with the height that decreases in the lateral direction awayfrom the at least one LED chip such that a portion of the lumiphoricmaterial layer is closer to the submount than the first side of the atleast one LED chip. In certain embodiments, a total height of the LEDpackage as measured from a mounting surface of the package bond pads tothe exterior light-exiting face is no more than 900 μm, or in a rangefrom 600 μm to 800 μm. In certain embodiments, the exteriorlight-exiting face for the LED package is configured to form aninterface with an ambient atmosphere that is separate from the LEDpackage. In certain embodiments, the lumiphoric material layer comprisesphosphor particles in a binder with a volume percentage of phosphorparticles in a range from 25% to 45%.

In another aspect, any of the foregoing aspects individually ortogether, and/or various separate aspects and features as describedherein, may be combined for additional advantage. Any of the variousfeatures and elements as disclosed herein may be combined with one ormore other disclosed features and elements unless indicated to thecontrary herein.

Those skilled in the art will appreciate the scope of the presentdisclosure and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 is a cross-sectional view of a typical light-emitting diode (LED)package that includes an LED chip on a submount.

FIG. 2 is a cross-sectional view of an LED package that is devoid oftypical encapsulation layers such that a surface of a lumiphoricmaterial layer forms an exterior light-exiting face for the LED package.

FIG. 3 is plot comparing near field emission intensity vs. inclinationangle for the LED package of FIG. 1 and the LED package of FIG. 2 .

FIG. 4 is a cross-sectional view of an LED package that is similar tothe LED package of FIG. 2 with an electrical connection arrangementbetween the LED chip and the submount.

FIG. 5 is a cross-sectional view of an LED package that is similar tothe LED package of FIG. 4 for embodiments where the light-alteringmaterial covers peripheral sidewalls of the LED chip and has a heightthat decreases in a lateral direction away from the LED chip.

FIG. 6A is a side view of an LED package that is similar to either theLED package of FIG. 4 or the LED package of FIG. 5 .

FIG. 6B is a top view of the LED package of FIG. 6A.

FIG. 6C is a bottom view of the LED package of FIG. 6A.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the embodiments andillustrate the best mode of practicing the embodiments. Upon reading thefollowing description in light of the accompanying drawing figures,those skilled in the art will understand the concepts of the disclosureand will recognize applications of these concepts not particularlyaddressed herein. It should be understood that these concepts andapplications fall within the scope of the disclosure and theaccompanying claims.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element such as a layer, region, orsubstrate is referred to as being “on” or extending “onto” anotherelement, it can be directly on or extend directly onto the other elementor intervening elements may also be present. In contrast, when anelement is referred to as being “directly on” or extending “directlyonto” another element, there are no intervening elements present.Likewise, it will be understood that when an element such as a layer,region, or substrate is referred to as being “over” or extending “over”another element, it can be directly over or extend directly over theother element or intervening elements may also be present. In contrast,when an element is referred to as being “directly over” or extending“directly over” another element, there are no intervening elementspresent. It will also be understood that when an element is referred toas being “connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present.

Relative terms such as “below” or “above” or “upper” or “lower” or“horizontal” or “vertical” may be used herein to describe a relationshipof one element, layer, or region to another element, layer, or region asillustrated in the Figures. It will be understood that these terms andthose discussed above are intended to encompass different orientationsof the device in addition to the orientation depicted in the Figures.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and/or “including” when used herein specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

Embodiments are described herein with reference to schematicillustrations of embodiments of the disclosure. As such, the actualdimensions of the layers and elements can be different, and variationsfrom the shapes of the illustrations as a result, for example, ofmanufacturing techniques and/or tolerances, are expected. For example, aregion illustrated or described as square or rectangular can haverounded or curved features, and regions shown as straight lines may havesome irregularity. Thus, the regions illustrated in the figures areschematic and their shapes are not intended to illustrate the preciseshape of a region of a device and are not intended to limit the scope ofthe disclosure. Additionally, sizes of structures or regions may beexaggerated relative to other structures or regions for illustrativepurposes and, thus, are provided to illustrate the general structures ofthe present subject matter and may or may not be drawn to scale. Commonelements between figures may be shown herein with common element numbersand may not be subsequently re-described.

Aspects disclose herein relate to light-emitting diode (LED) packagesand more particularly to LED packages with directional emissionintensity and color uniformity. LED packages include one or more LEDchips on a submount with arrangements of light-altering materials andlumiphoric material layers that provide directional light emissions withimproved color over angle uniformity. Light-altering materials areprovided that cover sidewalls of LED chips while lumiphoric materiallayers cover LED chips and light-altering materials. Such LED packagesmay avoid the need to include encapsulation materials and/or lenses thatwould otherwise cover the lumiphoric material layers. As such, exteriorlight-exiting faces of LED packages are formed by surfaces of lumiphoricmaterial layers.

Before delving into specific details of various aspects of the presentdisclosure, an overview of various elements that may be included inexemplary LEDs of the present disclosure is provided for context. An LEDchip typically comprises an active LED structure or region that can havemany different semiconductor layers arranged in different ways. Thefabrication and operation of LEDs and their active structures aregenerally known in the art and are only briefly discussed herein. Thelayers of the active LED structure can be fabricated using knownprocesses with a suitable process being fabrication using metal organicchemical vapor deposition. The layers of the active LED structure cancomprise many different layers and generally comprise an active layersandwiched between n-type and p-type oppositely doped epitaxial layers,all of which are formed successively on a growth substrate. It isunderstood that additional layers and elements can also be included inthe active LED structure, including, but not limited to, buffer layers,nucleation layers, super lattice structures, undoped layers, claddinglayers, contact layers, and current-spreading layers and lightextraction layers and elements. The active layer can comprise a singlequantum well, a multiple quantum well, a double heterostructure, orsuper lattice structures.

The active LED structure can be fabricated from different materialsystems, with some material systems being Group Ill nitride-basedmaterial systems. Group Ill nitrides refer to those semiconductorcompounds formed between nitrogen (N) and the elements in Group Ill ofthe periodic table, usually aluminum (Al), gallium (Ga), and indium(In). Gallium nitride (GaN) is a common binary compound. Group IIInitrides also refer to ternary and quaternary compounds such as aluminumgallium nitride (AlGaN), indium gallium nitride (InGaN), and aluminumindium gallium nitride (AlInGaN). For Group III nitrides, silicon (Si)is a common n-type dopant and magnesium (Mg) is a common p-type dopant.Accordingly, the active layer, n-type layer, and p-type layer mayinclude one or more layers of GaN, AlGaN, InGaN, and AlInGaN that areeither undoped or doped with Si or Mg for a material system based onGroup III nitrides. Other material systems include silicon carbide(SiC), organic semiconductor materials, and other Group III-V systemssuch as gallium phosphide (GaP), gallium arsenide (GaAs), indiumphosphide (InP), and related compounds.

The active LED structure may be grown on a growth substrate that caninclude many materials, such as sapphire, SiC, aluminum nitride (AlN),GaN, GaAs, glass, or silicon. SiC has certain advantages, such as acloser crystal lattice match to Group III nitrides than other substratesand results in Group III nitride films of high quality. SiC also has avery high thermal conductivity so that the total output power of GroupIII nitride devices on SiC is not limited by the thermal dissipation ofthe substrate. Sapphire is another common substrate for Group IIInitrides and also has certain advantages, including being lower cost,having established manufacturing processes, and having goodlight-transmissive optical properties.

Different embodiments of the active LED structure can emit differentwavelengths of light depending on the composition of the active layerand n-type and p-type layers. In some embodiments, the active LEDstructure emits blue light with a peak wavelength range of approximately430 nanometers (nm) to 480 nm. In other embodiments, the active LEDstructure emits green light with a peak wavelength range of 500 nm to570 nm. In other embodiments, the active LED structure emits red lightwith a peak wavelength range of 600 nm to 650 nm. In certainembodiments, the active LED structure may be configured to emit lightthat is outside the visible spectrum, including one or more portions ofthe ultraviolet (UV) spectrum.

An LED chip can also be covered with one or more lumiphoric materials(also referred to herein as lumiphors), such as phosphors, such that atleast some of the light from the LED chip is absorbed by the one or morelumiphors and is converted to one or more different wavelength spectraaccording to the characteristic emission from the one or more lumiphors.In this regard, at least one lumiphor receiving at least a portion ofthe light generated by the LED source may re-emit light having differentpeak wavelength than the LED source. An LED source and one or morelumiphoric materials may be selected such that their combined outputresults in light with one or more desired characteristics such as color,color point, intensity, spectral density, etc. In certain embodiments,aggregate emissions of LED chips, optionally in combination with one ormore lumiphoric materials, may be arranged to provide cool white,neutral white, or warm white light, such as within a color temperaturerange of 2500 Kelvin (K) to 10,000 K. In certain embodiments, lumiphoricmaterials having cyan, green, amber, yellow, orange, and/or red peakwavelengths may be used. In certain embodiments, the combination of theLED chip and the one or more lumiphors (e.g., phosphors) emits agenerally white combination of light. The one or more phosphors mayinclude yellow (e.g., YAG:Ce), green (e.g., LuAg:Ce), and red (e.g.,Ca_(i-x-y)Sr_(x)Eu_(y)AlSiN₃) emitting phosphors, and combinationsthereof. In other embodiments, the LED chip and corresponding lumiphoricmaterial may be configured to primarily emit converted light from thelumiphoric material so that aggregate emissions include little to noperceivable emissions that correspond to the LED chip itself.

Lumiphoric materials as described herein may be or include one or moreof a phosphor, a scintillator, a lumiphoric ink, a quantum dot material,a day glow tape, and the like. Lumiphoric materials may be provided byany suitable means, for example, direct coating on one or more surfacesof an LED, dispersal in an encapsulant material configured to cover oneor more LEDs, and/or coating on one or more optical or support elements(e.g., by powder coating, inkjet printing, or the like). In certainembodiments, lumiphoric materials may be downconverting or upconverting,and combinations of both downconverting and upconverting materials maybe provided. In certain embodiments, multiple different (e.g.,compositionally different) lumiphoric materials arranged to producedifferent peak wavelengths may be arranged to receive emissions from oneor more LED chips. One or more lumiphoric materials may be provided onone or more portions of an LED chip in various configurations. Incertain embodiments, lumiphoric materials may be provided over one ormore surfaces of LED chips, while other surfaces of such LED chips maybe devoid of lumiphoric material. In certain embodiments, a top surfaceof an LED chip may include lumiphoric material, while one or more sidesurfaces of an LED chip may be devoid of lumiphoric material. In certainembodiments, all or substantially all outer surfaces of an LED chip(e.g., other than contact-defining or mounting surfaces) may be coatedor otherwise covered with one or more lumiphoric materials. In certainembodiments, one or more lumiphoric materials may be arranged on or overone or more surfaces of an LED chip in a substantially uniform manner.In other embodiments, one or more lumiphoric materials may be arrangedon or over one or more surfaces of an LED chip in a manner that isnon-uniform with respect to one or more of material composition,concentration, and thickness. In certain embodiments, the loadingpercentage of one or more lumiphoric materials may be varied on or amongone or more outer surfaces of an LED chip. In certain embodiments, oneor more lumiphoric materials may be patterned on portions of one or moresurfaces of an LED chip to include one or more stripes, dots, curves, orpolygonal shapes. In certain embodiments, multiple lumiphoric materialsmay be arranged in different discrete regions or discrete layers on orover an LED chip.

As used herein, a layer or region of a light-emitting device may beconsidered to be “transparent” when at least 80% of emitted radiationthat impinges on the layer or region emerges through the layer orregion. Moreover, as used herein, a layer or region of an LED isconsidered to be “reflective” or embody a “mirror” or a “reflector” whenat least 80% of the emitted radiation that impinges on the layer orregion is reflected. In some embodiments, the emitted radiationcomprises visible light such as blue and/or green LEDs with or withoutlumiphoric materials. In other embodiments, the emitted radiation maycomprise nonvisible light. For example, in the context of GaN-based blueand/or green LEDs, silver (Ag) may be considered a reflective material(e.g., at least 80% reflective). In the case UV LEDs, appropriatematerials may be selected to provide a desired, and in some embodimentshigh, reflectivity and/or a desired, and in some embodiments low,absorption. In certain embodiments, a “light-transmissive”material maybe configured to transmit at least 50% of emitted radiation of a desiredwavelength.

The present disclosure can be useful for LED chips having a variety ofgeometries, such as vertical geometry or lateral geometry. A verticalgeometry LED chip typically includes anode and cathode connections onopposing sides or faces of the LED chip. A lateral geometry LED chiptypically includes both anode and cathode connections on the same sideof the LED chip that is opposite a substrate, such as a growthsubstrate. In certain embodiments, a lateral geometry LED chip may bemounted on a submount of an LED package such that the anode and cathodeconnections are on a face of the LED chip that is opposite the submount.In this configuration, wirebonds may be used to provide electricalconnections with the anode and cathode connections. In otherembodiments, a lateral geometry LED chip may be flip-chip mounted on asurface of a submount of an LED package such that the anode and cathodeconnections are on a face of the active LED structure that is adjacentto the submount. In this configuration, electrical traces or patternsmay be provided on the submount for providing electrical connections tothe anode and cathode connections of the LED chip. In a flip-chipconfiguration, the active LED structure is configured between thesubstrate of the LED chip and the submount for the LED package.Accordingly, light emitted from the active LED structure may passthrough the substrate in a desired emission direction. In otherembodiments, an active LED structure may be bonded to a carriersubmount, and the growth substrate may be removed such that light mayexit the active LED structure without passing through the growthsubstrate.

According to aspects of the present disclosure, LED packages may includeone or more elements, such as lumiphoric materials and electricalcontacts, among others, that are provided with one or more LED chips ona support member, such as a submount or a lead frame. Suitable materialsfor the submount include, but are not limited to, ceramic materials suchas aluminum oxide or alumina, AlN, or organic insulators like polyimide(PI) and polyphthalamide (PPA). In other embodiments, a submount maycomprise a printed circuit board (PCB), sapphire, Si or any othersuitable material. For PCB embodiments, different PCB types can be usedsuch as standard FR-4 PCB, metal core PCB, or any other type of PCB. Instill further embodiments, the support structure may embody a lead framestructure. Light-altering materials may be arranged within LED packagesto reflect or otherwise redirect light from the one or more LED chips ina desired emission direction or pattern.

As used herein, light-altering materials may include many differentmaterials including light-reflective materials that reflect or redirectlight, light-absorbing materials that absorb light, and materials thatact as a thixotropic agent. As used herein, the term “light-reflective”refers to materials or particles that reflect, refract, scatter, orotherwise redirect light. For light-reflective materials, thelight-altering material may include at least one of fused silica, fumedsilica, titanium dioxide (TiO₂), or metal particles suspended in abinder, such as silicone or epoxy. In certain aspects, the particles mayhave an index or refraction that is configured to refract lightemissions in a desired direction. In certain aspects, light-reflectiveparticles may also be referred to as light-scattering particles. Aweight ratio of the light-reflective particles or scattering particlesto a binder may comprise a range of about 0.15:1 to about 0.5:1, or in arange of about 0.5:1 to about 1:1, or in a range of about 1:1 to about2:1, depending on a desired viscosity before curing. For light-absorbingmaterials, the light-altering material may include at least one ofcarbon, silicon, or metal particles suspended in a binder, such assilicone or epoxy. The light-reflective materials and thelight-absorbing materials may comprise nanoparticles. In certainembodiments, the light-altering material may comprise a generally whitecolor to reflect and redirect light. In other embodiments, thelight-altering material may comprise a generally opaque color, such asblack or gray for absorbing light and increasing contrast. In certainembodiments, the light-altering material includes both light-reflectivematerial and light-absorbing material suspended in a binder.

Embodiments of the present disclosure are applicable to LED packagesthat include multiple LED chips clustered together to provide increasedlight output and/or the capability for a single LED package to emitmultiple colors and/or peak wavelengths of light. Relative sizes orareas of individual LED chips within an LED package may be selectedaccording to desired emission intensities and profiles. In certainembodiments, the LED chips within an LED package may have smaller sizessuch as 0.5 millimeters (mm) by 0.5 mm and/or larger sizes such as 2 mmby 2 mm, or other ranges from 0.5 mm by 0.5 mm to 1 mm by 1 mm. Incertain embodiments, a longest lateral dimension of each LED chip may bein a range from 0.5 mm to 2 mm, or in a range from 1 mm to 2 mm, or in arange from 0.5 mm to 1 mm. In such ranges where at least one dimensionis 0.5 mm and greater, the LED chips may be well suited for providinghigh output powers in a compact footprint.

Despite advances in LED packaging technology, challenges remain indirecting light emissions from LED chips and/or lumiphoric materials indesired directions with increased efficacy and suitable coloruniformity. Light emissions that are generated within active regions ofLEDs and wavelength-converted light from lumiphoric materials may beomnidirectional in nature. In this regard, light may attempt to exit allsides of an LED chip within a package, thereby contributing to emissionpatterns with intensities that vary over wide emission angles.Additionally, laterally emitted light may interact differently withlumiphoric materials to contribute to reduced color over angleuniformity. According to aspects of the present disclosure,light-altering material arrangements are provided proximate toperipheral edges or sidewalls of LED chips that redirect laterallyemitted light in desired light-emitting directions, such as toward a topsurface of the LED chip that is opposite a mounting surface for the LEDchip. In this manner, such light-altering material arrangements mayprovide a two-dimensional light-emitting surface for LED chips, ratherthan three-dimensional light-emitting surfaces when light is allowed toexit LED chip sidewalls. According to further aspects of the presentdisclosure, lumiphoric material arrangements are provided in such amanner that allows traditional encapsulation layers and/or lenses to beomitted. In this regard, a surface of a lumiphoric material isconfigured to form an exterior light-exiting surface for the LEDpackage. By providing such lumiphoric material arrangements, light fromLED chips may pass through fewer interfaces and travel shorter distanceswhen exiting the package, thereby providing enhanced directional lightintensity and color uniformity.

FIG. 1 is a cross-sectional view of a typical LED package 10 thatincludes an LED chip 12 on a submount 14. The LED chip 12 furtherincludes a lumiphoric material layer 16 that covers the LED chip 12 onthe submount 14. In this regard, a first side 12′ of the LED chip 12 maybe provided adjacent or closer to the lumiphoric material layer 16 whilea second side 12″ of the LED chip 12 is mounted to the submount 14. TheLED chip 12 further includes an encapsulation layer 18 that islight-transmissive or light-transparent to wavelengths of light from theLED chip 12 and the lumiphoric material layer 16. The encapsulationlayer 18 is typically arranged to provide environmental protection forthe underlying elements of the LED package 10 and, in certainapplications, a shape of the encapsulation layer 18 may be configured toshape light emission patterns from the LED package 10. A typicalmaterial for the encapsulation layer 18 may be silicone or a resin. Asillustrated by the arrows of FIG. 1 , light 20 exits the LED package 10through surfaces of the encapsulation layer 18. In this manner, theouter surfaces of the encapsulation layer form exterior light-exitingfaces 10 _(LEF) for the LED package 10.

With such an arrangement, portions of the light 20 generated by the LEDchip 12 must pass through at least a first internal interface formedbetween the LED chip 12 and the lumiphoric material layer 16 and asecond internal interface formed between the lumiphoric material layer16 and the encapsulation layer 18 before reaching the exteriorlight-exiting faces 10 _(LEF). Additionally, portions of the light 20that are subject to wavelength conversion within the lumiphoric materiallayer 16 must pass through at least the above-described second internalinterface before reaching the exterior light-exiting faces 10 _(LEF). Ateach internal interface or the exterior light-exiting faces 10 _(LEF),the light 20 has an opportunity to reflect or refract away from adesired emission direction that is normal to the surface of the submount14 on which the LED chip 12 is mounted. Additionally, a near fieldemission intensity of the light 20 can be relatively high at higheremission angles, such as greater than 60 degrees from a lineperpendicular to the surface of the submount 14 on which the LED chip 12is mounted. In this manner, a significant portion of light may laterallyescape the LED package 10. Furthermore, such laterally emitted light mayhave reduced color mixing of light from the LED chip 12 and thelumiphoric material layer 16.

FIG. 2 is a cross-sectional view of an LED package 22 that is devoid oftypical encapsulation layers such that a surface of the lumiphoricmaterial layer 16 forms an exterior light-exiting face 22 _(LEF) for theLED package 22. As illustrated, the LED package 22 includes the LED chip12 on a first side 14′ of the submount 14 that is opposite a second side14″ of the submount 14. The LED chip 12 may be provided such that alateral width of the LED chip 12 is less than a corresponding lateralwidth of the submount 14. A light-altering material 24, such as alight-reflecting and/or light refracting material as described above,may be arranged on portions of the submount 14 that are adjacent the LEDchip 12. In certain embodiments, the light-altering material 24 may bearranged to extend all the way to peripheral edges 14E of the submount14. In still further embodiments, the light-altering material 24 maycover all surfaces of the first side 14′ of the submount 14 that areoutside the LED chip 12. In this manner, laterally-emitted light fromthe LED chip 12 may be redirected toward a desired emission directionfor the LED package 22 that is along a perpendicular direction from thefirst side 14′ of the submount 14. In doing so, challenges associatedwith color mixing uniformity along package edges may be improved.

As further illustrated in FIG. 2 , the lumiphoric material layer 16 isarranged on the LED chip 12 and the light-altering material 24. In thismanner, the lumiphoric material layer 16 is arranged to cover the LEDchip 12 and laterally extend across portions of the light-alteringmaterial 24 adjacent to the LED chip 12. In certain embodiments, thelumiphoric material layer 16 may be arranged to laterally extend all theway to the peripheral edges 14E of the submount 14 in a similar manneras the light-altering material 24. In this regard, the light-alteringmaterial 24 may be arranged between the lumiphoric material layer 16 andthe submount 14. Additionally, portions of the lumiphoric material layer16, the light-altering material 24, and the submount 14 may collectivelyform a peripheral edge of the LED package 22. Such an arrangement may beprovided by mounting a plurality of LED chips 12 across a largersubmount panel, applying the light-altering material 24 along portionsof the submount panel outside the LED chips 12, and applying thelumiphoric material layer 16 to cover the LED chips 12 and thelight-altering material 24. In certain aspects, the lumiphoric materiallayer 16 may include lumiphoric particles in a binder that isspray-coated, dispensed, or otherwise applied to the LED chips beforecuring of the binder. Individual LED packages 22 may be formed by asingulating or dicing step that separates the larger submount panel intoindividual packages.

By omitting typical encapsulation layers that would be above thelumiphoric material layer 16, the exterior light-exiting face 22 _(LEF)for the LED package 22 is provided by a surface of the lumiphoricmaterial layer 16, thereby reducing a number of interfaces that light 20must pass through before exiting the LED package 22. The exteriorlight-exiting face 22 _(LEF) may thereby form an interface between theLED package 22 and a surrounding environment that is separate from theLED package 22. For example, the surrounding environment may embody anopen ambient atmosphere that is exposed for indoor and/or outdoorenvironments or an enclosed and/or partially enclosed ambient atmospherethat is within another device, such as a portion of a lighting fixturein which the LED package 22 is arranged. By extending the lumiphoricmaterial layer 16 all the way to the peripheral edges 14E of thesubmount 14, the exterior light-exiting face 22 _(LEF) may thereby beextended across the entire submount 14. Typical encapsulation layerswould provide environmental protection for underlying elements of theLED package 22. By having the lumiphoric material layer 16 form theexterior light-exiting face 22 _(LEF), the lumiphoric material layer 16itself may be configured to provide the environmental protection alongwith wavelength conversion.

In certain embodiments, the lumiphoric material layer 16 may compriselumiphoric particles within a binder material, with a specific examplebeing phosphor particles within a binder material of silicone or resin.When spray-coated or dispensed as described above, the distribution oflumiphoric particle sizes may form an uneven or bumpy surface forlumiphoric material layers. These uneven surfaces are typically coveredby encapsulation layers since if exposed, the uneven surfaces couldpromote handing failures when contacted. According to principles of thepresent disclosure, a loading of lumiphoric particles relative to abinder material for the lumiphoric material layer 16 may be configuredto provide suitable wavelength conversion while also forming a smoothupper surface of the lumiphoric material layer 16. This smooth uppersurface corresponds with the exterior light-exiting face 22 _(LEF) ofthe LED package 22. By forming the smooth upper surface of thelumiphoric material layer 16, the LED package 22 may be moremechanically robust to provide the environmental protection typicallyprovided by encapsulation layers.

In certain embodiments, the loading may comprise a weight ratio oflumiphoric particles to the binder material that is in a range from 1.5to 2.5. In specific examples, a weight ratio of 1.5 may correspond withthe lumiphoric material layer 16 having a volume of 29% lumiphoricparticles to 71% binder material, or a weight that is 60% lumiphoricmaterials and 40% binder material. A weight ratio of 2.5 may correspondwith the lumiphoric material layer having a volume of 41% lumiphoricparticles to 59% binder material, or a weight that is 71% lumiphoricmaterials and 28% binder material. In certain embodiments, thelumiphoric material layer 16 may include a volume percentage oflumiphoric particles in a range from 25% to 45% or a weight percentageof lumiphoric particles in a range from 55% to 75% to provide a smoothupper surface for the exterior light-exiting face 22 _(LEF). Higherloading of lumiphoric particles may contribute to the uneven surfacesdescribed above, while lower loading may not provide suitable wavelengthconversion without having to substantially increase a thickness of thelumiphoric material layer 16. In certain embodiments, a thickness of thelumiphoric material layer 16 as measured from the LED chip 12 may be nomore than 150 microns (μm), or no more than 100 μm, or in a range from50 μm to 100 μm. In this regard, a perpendicular distance from the firstside 12′ of the LED chip 12 to the exterior light-exiting face 22 _(LEF)may be no more than 150 μm, or no more than 100 μm, or in a range from50 μm to 100 μm in certain embodiments. As such, a portion of thelumiphoric material layer 16 may form the exterior light-exiting face 22_(LEF) of the LED package 22, while still maintaining an overall slimprofile for the LED package 22. In combination with the arrangement ofthe light-altering material 24, the LED package 22 may exhibit increasedlight emissions with improved color uniformity compared with the LEDpackage 10 of FIG. 1 . In certain embodiments, the thickness valuesdescribed above for the lumiphoric material layer 16 may be no more than100 μm for overall emission targets with color temperatures in the 2700K to 7000 K range, while thickness values of no more than 150 μm may bewell suited for color temperatures below 2700 K, such as in a range from1800 K to 2400 K. In still further embodiments, saturated emissionswhere a substantial majority of emissions are provided from wavelengthconversion in the lumiphoric material layer 16 may have thickness valuesfor the lumiphoric material layer 16 of no more than 150 μm. By way ofexample, an embodiment with saturated emissions for the LED package 22may include the LED chip 12 being configured to provide blue emissionsand the lumiphoric material layer 16 being configured to covert asubstantial majority of the blue emissions, such as greater than 90%, orgreater than 95%, or greater than 99%, to another color, such as amber.

FIG. 3 is plot comparing near field emission intensity vs. inclinationangle for the LED package 10 of FIG. 1 and the LED package 22 of FIG. 2. The y-axis represents light intensity in arbitrary units and thex-axis represents inclination angle as measured from a direction that isnormal to a center of the first side 12′ of the LED chip 12 of FIGS. 1and 2 . A 0° inclination angle corresponds to light intensity along thedirection normal to the first side 12′ while a 90° inclination anglecorresponds with light intensity laterally emitted along edges of theLED package (10 or 22) along a direction that is parallel to the firstside 12′. As illustrated, the LED package 22 of FIG. 2 exhibitsincreased light intensity for inclination angles below about 15°, whilethe LED package 10 exhibits increased lateral emissions. In this regard,the arrangement of the lumiphoric material layer 16 as the exteriorlight-exiting face 22 _(LEF) of the LED package 22 in combination withthe light-altering material 24 of FIG. 2 provides improved directionalemission intensity.

FIG. 4 is a cross-sectional view of an LED package 26 that is similar tothe LED package 22 of FIG. 2 with an electrical connection arrangementbetween the LED chip 12 and the submount 14. The first side 14′ of thesubmount 14 may include a number of metal traces 28-1 to 28-2, and thesecond side 14″ of the submount 14 may include a number of package bondpads 30-1 to 30-2 that are electrically coupled to the metal traces 28-1to 28-2. In certain embodiments, a number of electrically conductivevias 32 may extend through the submount 14 to electrically couple thepackage bond pads 30-1 to 30-2 to the metal traces 28-1 to 28-2. Firstand second contacts 34-1 to 34-2 of the LED chip 12 may be electricallycoupled to respective ones of the metal traces 28-1 to 28-2. As such,the first contact 34-1, the metal trace 28-1, one or more of theelectrically conductive vias 32, and the package bond pad 30-1 may forman electrically conductive anode path while the second contact 34-2, themetal trace 28-2, one or more of the electrically conductive vias 32,and the package bond pad 30-2 may form an electrically conductivecathode path. In other embodiments, the order of the anode and cathodepaths may be reversed. As illustrated in FIG. 4 , the first and secondcontacts 34-1 to 34-2 may be arranged on the second side 12″ of the LEDchip 12 such that the LED chip 12 may embody a flip-chip LED that isflip-chip mounted and electrically coupled with the metal traces 28-1 to28-2. In other embodiments, the LED chip 12 may embody other geometriessuch that wire bond connections are employed between the LED chip 12 andthe metal traces 28-1 to 28-2. As previously described, the lumiphoricmaterial layer 16 may form an exterior light-exiting face 26 _(LEF) ofthe LED package 26 and in combination with the light-altering material24, improved directional emission intensity and uniformity may beachieved. A thickness 16T of the lumiphoric material layer 16 asmeasured from the LED chip 12 may be no more than 100 μm or in a rangefrom 50 μm to 100 μm as previously described. Depending on dimensions ofthe submount 14 and LED chip 12, a total height 26H of the LED package26 as measured from a mounting surface of the package bond pads 30-1 to30-2 to the exterior light-exiting face 26 _(LEF) may be no more than900 μm or in a range from 600 μm to 800 μm.

FIG. 5 is a cross-sectional view of an LED package 36 that is similar tothe LED package 26 of FIG. 4 for embodiments where the light-alteringmaterial 24 covers peripheral sidewalls of the LED chip 12 and has aheight that decreases in a lateral direction away from the LED chip 12.In certain embodiments, the light-altering material 24 may be arrangedwith a top surface that is sloped in a direction away from the LED chip12. For example, the light-altering material 24 may be applied bydispensing in such a way that the peripheral edges of the LED chip 12are covered while a height of the light-altering material 24 above thesubmount 14 decreases in a lateral direction away from the peripheraledges of the LED chip 12. As illustrated, a first height 24 _(H1) of thelight-altering material 24 is at or near a height of the first side 12′of the LED chip 12 above the submount 14 while a second height 24 _(H2)of the light-altering material 24 is less than the first height 24_(H1). This arrangement may be accomplished by selection of a viscosityof the light-altering material 24 before curing and from surface tensionwith the peripheral edges of the LED chip 12 while the remainder of thelight-altering material 24 settles to a lower height. In this regard,formation of the light-altering material 24 along the first side 12′, ortop surface, of the LED chip 12 may be discouraged. In such embodiments,the light-altering material 24 may be formed with reduced lateralthickness, particularly in regions at or near the first side 12′ of theLED chip 12, and some laterally propagating light in these regions mayescape the light-altering material 24 without being redirected. Asillustrated, the lumiphoric material layer 16 is arranged to extend onportions of the light-altering material 24 between the first height 24_(H1) and the second height 24 _(H2) such that a portion of thelumiphoric material layer 16 is closer to the submount 14 than the firstside 12′ of the LED chip 12. In this regard, any light that may escapethe reduced lateral thickness regions of the light-altering material 24may be subject to wavelength conversion, thereby improving color overangle emission uniformity.

In alternative embodiments, the LED package 26 of FIG. 4 or the LEDpackage 36 of FIG. 5 may be configured to provide monochromaticemissions. In such embodiments, the lumiphoric material layer 16 may beomitted such that the first side 12′ of the LED chip 12 forms theexterior light-exiting face (26 _(LEF) or 36 _(LEF)) in either the LEDpackage 26 of FIG. 4 or the LED package 36 of FIG. 5 .

FIGS. 6A to 6C illustrate various view of an LED package 38 that issimilar to either the LED package 26 of FIG. 4 or the LED package 36 ofFIG. 5 . FIG. 6A is a side view of the LED package 38 illustrating aslim profile thereof. From the side view, portions of the submount 14,the light-altering material 24, and the lumiphoric material layer 16collectively form peripheral edges of the LED package 38. From this sideview, the package bond pad 30-1 is also visible. FIG. 6B is a top viewof the LED package 38 of FIG. 6A. Since the lumiphoric material layer 16is arranged to extend all the way to the peripheral edges of thesubmount 14, only the lumiphoric material layer 16 is visible from thetop view in certain embodiments. In this manner, an exteriorlight-exiting face 38 _(LEF) of the lumiphoric material layer 16 is allthat is visible. FIG. 6C is a bottom view of the LED package 38 of FIG.6A illustrating two package bond pads 30-1 to 30-2. In certainembodiments, the package bond pads 30-2 may have a notch or other shapethat distinguishes it from the other package bond pad 30-1 to serve as apolarity indicator for proper mounting of the LED package 38.

It is contemplated that any of the foregoing aspects, and/or variousseparate aspects and features as described herein, may be combined foradditional advantage. Any of the various embodiments as disclosed hereinmay be combined with one or more other disclosed embodiments unlessindicated to the contrary herein.

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present disclosure. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

What is claimed is:
 1. A light-emitting diode (LED) package comprising:a submount; at least one LED chip on the submount, the at least one LEDchip including a first side, a second side that is mounted to thesubmount, and peripheral edges that bound the first side and the secondside; a light-altering material on the peripheral edges of the at leastone LED chip and on portions of the submount that are adjacent the atleast one LED chip; and a lumiphoric material layer on the at least oneLED chip and the light-altering material, wherein a surface of thelumiphoric material layer forms an exterior light-exiting face for theLED package.
 2. The LED package of claim 1, wherein the lumiphoricmaterial layer, the light-altering material, and the submountcollectively form a peripheral edge of the LED package.
 3. The LEDpackage of claim 1, wherein the lumiphoric material layer comprises athickness of no more than 150 microns (μm).
 4. The LED package of claim3, wherein the thickness of the lumiphoric material layer is in a rangefrom 50 μm to 100 μm.
 5. The LED package of claim 1, wherein aperpendicular distance from the first side of the LED chip to theexterior light-exiting face is no more than 100 microns (μm).
 6. The LEDpackage of claim 5, wherein the perpendicular distance from the firstside of the LED chip to the exterior light-exiting face is in a rangefrom 50 μm to 100 μm.
 7. The LED package of claim 1, wherein thelight-altering material covers the peripheral edges of the at least oneLED chip.
 8. The LED package of claim 7, wherein a height of thelight-altering material above the submount decreases in a lateraldirection away from the peripheral edges of the at least one LED chip.9. The LED package of claim 8, wherein the lumiphoric material layerextends on a portion of the light-altering material with the height thatdecreases in the lateral direction away from the peripheral edges of theat least one LED chip such that a portion of the lumiphoric materiallayer is closer to the submount than the first side of the at least oneLED chip.
 10. The LED package of claim 1, wherein the lumiphoricmaterial layer comprises phosphor particles in a binder with a volumepercentage of phosphor particles in a range from 25% to 45%.
 11. The LEDpackage of claim 1, wherein the exterior light-exiting face for the LEDpackage is configured to form an interface with an ambient atmospherethat is separate from the LED package.
 12. A light-emitting diode (LED)package comprising: a submount comprising a first side and a second sidethat opposes the first side, the first side comprising metal traces, andthe second side comprising package bond pads that are electricallycoupled to the metal traces; at least one LED chip including a firstside and a second side that is mounted on and electrically coupled tothe metal traces; and a lumiphoric material layer on the at least oneLED chip such that a surface of the lumiphoric material layer forms anexterior light-exiting face for the LED package and a perpendiculardistance from the first side of the LED chip to the exteriorlight-exiting face is no more than 100 microns (μm).
 13. The LED packageof claim 12, wherein the perpendicular distance from the first side ofthe LED chip to the exterior light-exiting face is in a range from 50 μmto 100 μm.
 14. The LED package of claim 12, further comprising alight-altering material on portions of the submount that are adjacentthe at least one LED chip, wherein the light-altering material isarranged between the lumiphoric material layer and the submount.
 15. TheLED package of claim 14, wherein a height of the light-altering materialabove the submount decreases in a lateral direction away from the atleast one LED chip.
 16. The LED package of claim 15, wherein thelumiphoric material layer extends on a portion of the light-alteringmaterial with the height that decreases in the lateral direction awayfrom the at least one LED chip such that a portion of the lumiphoricmaterial layer is closer to the submount than the first side of the atleast one LED chip.
 17. The LED package of claim 12, wherein a totalheight of the LED package as measured from a mounting surface of thepackage bond pads to the exterior light-exiting face is no more than 900μm.
 18. The LED package of claim 17, wherein the total height is in arange from 600 μm to 800 μm.
 19. The LED package of claim 12, whereinthe exterior light-exiting face for the LED package is configured toform an interface with an ambient atmosphere that is separate from theLED package.
 20. The LED package of claim 12, wherein the lumiphoricmaterial layer comprises phosphor particles in a binder with a volumepercentage of phosphor particles in a range from 25% to 45%.